/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.db.mpp.execution.operator.process.last;

import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import org.apache.iotdb.db.mpp.execution.operator.Operator;
import org.apache.iotdb.db.mpp.execution.operator.OperatorContext;
import org.apache.iotdb.db.mpp.execution.operator.process.ProcessOperator;
import org.apache.iotdb.tsfile.common.conf.TSFileDescriptor;
import org.apache.iotdb.tsfile.read.common.block.TsBlock;
import org.apache.iotdb.tsfile.read.common.block.TsBlockBuilder;
import org.apache.iotdb.tsfile.utils.Binary;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.concurrent.TimeUnit;

import static com.google.common.util.concurrent.Futures.successfulAsList;
import static org.apache.iotdb.db.mpp.execution.operator.process.last.LastQueryUtil.compareTimeSeries;
import static org.apache.iotdb.tsfile.read.common.block.TsBlockBuilderStatus.DEFAULT_MAX_TSBLOCK_SIZE_IN_BYTES;

// collect all last query result in the same data region and sort them according to the
// time-series's alphabetical order
public class LastQuerySortOperator implements ProcessOperator {
    private static final int MAX_DETECT_COUNT =
            TSFileDescriptor.getInstance().getConfig().getMaxTsBlockLineNumber();

    // we must make sure that data in cachedTsBlock has already been sorted
    // values that have last cache
    private TsBlock cachedTsBlock;

    private final int cachedTsBlockSize;

    // read index for cachedTsBlock
    private int cachedTsBlockRowIndex;

    // we must make sure that Operator in children has already been sorted
    private final List<AbstractUpdateLastCacheOperator> children;

    private final OperatorContext operatorContext;

    private final int inputOperatorsCount;

    private int currentIndex;

    private final TsBlockBuilder tsBlockBuilder;

    private final Comparator<Binary> timeSeriesComparator;

    // used to cache previous TsBlock get from children
    private TsBlock previousTsBlock;

    private int previousTsBlockIndex = 0;

    public LastQuerySortOperator(
            OperatorContext operatorContext,
            TsBlock cachedTsBlock,
            List<AbstractUpdateLastCacheOperator> children,
            Comparator<Binary> timeSeriesComparator) {
        this.cachedTsBlock = cachedTsBlock;
        this.cachedTsBlockSize = cachedTsBlock.getPositionCount();
        this.operatorContext = operatorContext;
        this.children = children;
        this.inputOperatorsCount = children.size();
        this.currentIndex = 0;
        this.tsBlockBuilder = LastQueryUtil.createTsBlockBuilder();
        this.timeSeriesComparator = timeSeriesComparator;
        this.previousTsBlock = null;
    }

    @Override
    public OperatorContext getOperatorContext() {
        return operatorContext;
    }

    @Override
    public ListenableFuture<?> isBlocked() {
        if (currentIndex < inputOperatorsCount) {
            int endIndex = getEndIndex();
            List<ListenableFuture<?>> listenableFutures = new ArrayList<>();
            for (int i = currentIndex; i < endIndex; i++) {
                ListenableFuture<?> blocked = children.get(i).isBlocked();
                if (!blocked.isDone()) {
                    listenableFutures.add(blocked);
                }
            }
            return listenableFutures.isEmpty() ? NOT_BLOCKED : successfulAsList(listenableFutures);
        } else {
            return Futures.immediateVoidFuture();
        }
    }

    @Override
    public TsBlock next() {
        // we have consumed up data from children Operator, just return all remaining cached data in
        // cachedTsBlock, tsBlockBuilder and previousTsBlock
        if (currentIndex >= inputOperatorsCount) {
            if (previousTsBlock != null) {
                while (previousTsBlockIndex < previousTsBlock.getPositionCount()) {
                    if (canUseDataFromCachedTsBlock(previousTsBlock, previousTsBlockIndex)) {
                        LastQueryUtil.appendLastValue(tsBlockBuilder, cachedTsBlock, cachedTsBlockRowIndex++);
                    } else {
                        LastQueryUtil.appendLastValue(tsBlockBuilder, previousTsBlock, previousTsBlockIndex++);
                    }
                }
            }
            TsBlock res = cachedTsBlock.subTsBlock(cachedTsBlockRowIndex);
            cachedTsBlockRowIndex = cachedTsBlockSize;
            if (!tsBlockBuilder.isEmpty()) {
                LastQueryUtil.appendLastValue(tsBlockBuilder, res);
                res = tsBlockBuilder.build();
                tsBlockBuilder.reset();
            }
            return res;
        }

        // start stopwatch
        long maxRuntime = operatorContext.getMaxRunTime().roundTo(TimeUnit.NANOSECONDS);
        long start = System.nanoTime();

        int endIndex = getEndIndex();

        while ((System.nanoTime() - start < maxRuntime)
                && (currentIndex < endIndex
                || (previousTsBlock != null
                && previousTsBlockIndex < previousTsBlock.getPositionCount()))
                && !tsBlockBuilder.isFull()) {
            if (previousTsBlock == null || previousTsBlock.getPositionCount() <= previousTsBlockIndex) {
                if (children.get(currentIndex).hasNextWithTimer()) {
                    previousTsBlock = children.get(currentIndex).nextWithTimer();
                    previousTsBlockIndex = 0;
                    if (previousTsBlock == null) {
                        return null;
                    }
                }
                currentIndex++;
            }
            if (previousTsBlockIndex < previousTsBlock.getPositionCount()) {
                if (canUseDataFromCachedTsBlock(previousTsBlock, previousTsBlockIndex)) {
                    LastQueryUtil.appendLastValue(tsBlockBuilder, cachedTsBlock, cachedTsBlockRowIndex++);
                } else {
                    LastQueryUtil.appendLastValue(tsBlockBuilder, previousTsBlock, previousTsBlockIndex++);
                }
            }
        }

        TsBlock res = tsBlockBuilder.build();
        tsBlockBuilder.reset();
        return res;
    }

    @Override
    public boolean hasNext() {
        return currentIndex < inputOperatorsCount
                || cachedTsBlockRowIndex < cachedTsBlockSize
                || !tsBlockBuilder.isEmpty()
                || (previousTsBlock != null && previousTsBlockIndex < previousTsBlock.getPositionCount());
    }

    @Override
    public void close() throws Exception {
        for (Operator child : children) {
            child.close();
        }
        cachedTsBlock = null;
    }

    @Override
    public boolean isFinished() {
        return !hasNextWithTimer();
    }

    @Override
    public long calculateMaxPeekMemory() {
        long maxPeekMemory = DEFAULT_MAX_TSBLOCK_SIZE_IN_BYTES + cachedTsBlock.getRetainedSizeInBytes();
        long res = 0;
        for (Operator child : children) {
            res = Math.max(res, maxPeekMemory + child.calculateMaxPeekMemory());
        }
        return res;
    }

    @Override
    public long calculateMaxReturnSize() {
        return DEFAULT_MAX_TSBLOCK_SIZE_IN_BYTES;
    }

    @Override
    public long calculateRetainedSizeAfterCallingNext() {
        long childrenMaxReturnSize = 0;
        long childrenSumRetainedSize = 0;
        for (Operator child : children) {
            childrenMaxReturnSize = Math.max(childrenMaxReturnSize, child.calculateMaxReturnSize());
            childrenSumRetainedSize += child.calculateRetainedSizeAfterCallingNext();
        }
        return cachedTsBlock.getRetainedSizeInBytes() + childrenMaxReturnSize + childrenSumRetainedSize;
    }

    private int getEndIndex() {
        return currentIndex + Math.min(MAX_DETECT_COUNT, inputOperatorsCount - currentIndex);
    }

    private boolean canUseDataFromCachedTsBlock(TsBlock tsBlock, int index) {
        return cachedTsBlockRowIndex < cachedTsBlockSize
                && compareTimeSeries(
                cachedTsBlock, cachedTsBlockRowIndex, tsBlock, index, timeSeriesComparator)
                < 0;
    }
}
